Edit by frankenduck: This topic only applies to 93 and earlier 4V K bikes. (K100RS4V, K1 & 93- K1100s.) I'm putting this in the General Maintenance category at the top because it is an almost always overlooked, yet relatively simple and inexpensive, maintenance item to keep your bike running well. I recommend doing it at least every 25,000 miles or so - or when you pull the battery out to replace it or do a spline lube since you'll have easy access to it. If you're unsure if it's ever been done then you might want to consider doing it in the relatively near future as preventative maintenance. If you plan on syncing your throttle bodies at the same time then do this before you sync the throttle bodies as you want the engine running at it's best when you sync the TBs.
The 93 and earlier 4V K bikes have an ignition amplifier (part # 12141461441) located on the front lower left of the bracket that holds the battery. It's purpose is to boost the signal from the Motronic to the ignition coils. In order to stay cool under operation it uses the battery bracket as a heat sink. To facilitate heat transfer from the ignition amp to the bracket there's a layer of heat sink compound between the ignition amp and the bracket.
Over time and use the heat sink compound breaks down and loses it's efficacy. The result of this is that the ignition amp overheats and does not function properly. The usual symptom is that the coils don't fire properly and the engine will run slightly roughly(noticeable at idle if you're paying attention) and eventually, as it gets worse, sputter periodically. In my experience, if the HS compound hasn't been refreshed since the bike left the factory, this problem usually manifests itself somewhere around 75-80k miles although, given how old these bikes are getting, it may manifest itself sooner.
Heat sink compound is a more or less generic product commonly used in electronic and automotive applications and can be purchased for just a few $$$ at Radio Shack or an auto parts store.
Here's lhead's original post - thanks. (with a few added notes from me)
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Last night, per Duck's advice, I removed the ignition module and renewed the coating of heat sink compound that serves to help keep the module cool when mounted on the front of the battery box. Here's a short tutorial. Sorry, there's no pictures, but it's not difficult.
Tools needed:
Flat head screwdriver.
10mm box end wrench
#1 and #1 Phillips screwdrivers
4mm allen wrench
7mm box end wrench
(Helpful) Needlenose pliers and needlenose vice grips
Heat Sink Compound (Radio Shack p.n. 276-1372)
1. Remove left and right side covers.
2. Open seat.
3. Remove Motronic connector.
4. Remove 3 allen head screws and remove Motronic module.
5. Remove two long battery hold down bolts.
6. Lift battery hold down bracket with ABS computer attached up and to the rear to clear battery.
7. Disconnect and remove battery.
8. Holding onto nuts in front of the ignition module with box end wrench or needlenose Vice Grips, remove flathead screws from inside battery box.
9. Pull module away from battery box. Note dried up cruddy compound.
10 Wipe module's mounting surface and surface of battery box with alcohol to clean aforementioned compound. (I use steel wool or a wire brush to get the metal really clean and then wipe it down with rubbing alcohol.)
11. Using finger, apply a thin coating of heat sink compound to module. (Use lots of it and once the ignition amp is re-attached wipe off any excess that gets squeezed out.)
As the manuals are fond of saying, assembly is the reverse of disassembly.
This seems to have helped my the missing I've been experiencing off idle recently. At least it behaved on the ride into work today.
Hope this helps,
Charlie
1993 K1100rs
